Particulate matter dynamics in naturally ventilated freestall dairy barns

Particulate matter (PM) concentrations and ventilation rates, in two naturally ventilated freestall dairy barns, were continuously monitored for two years. The first barn (B1) housed 400 fresh lactating cows, while the second barn (B2) housed 835 non-fresh lactating cows and 15 bulls. The relationships between PM concentrations and accepted governing parameters (environmental conditions and cattle activity) were examined. In comparison with other seasons, PM concentrations were lowest in winter. Total suspended particulate (TSP) concentrations in spring and autumn were relatively higher than those in summer. Overall: the concentrations in the barns and ambient air, for all the PM categories (PM2.5, PM10, and TSP), exhibited non-normal positively skewed distributions, which tended to overestimate mean or average concentrations. Only concentrations of PM2.5 and PM10 increased with ambient air temperature (R2 = 0.60–0.82), whereas only concentrations of TSP increased with cattle activity. The mean respective emission rates of PM2.5, PM10, and TSP for the two barns ranged between 1.6–4.0, 11.9–15.0, and 48.7–52.5 g d−1 cow−1, indicating similar emissions from the two barns.